First step to remove SingleRequestHostResolver.

net/dns/host_resolver_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 1301 matching lines @@
       KillDnsTask();
       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
                                         ERR_ABORTED);
     } else if (is_queued()) {
       // |resolver_| was destroyed without running this Job.
       // TODO(szym): is there any benefit in having this distinction?
       net_log_.AddEvent(NetLog::TYPE_CANCELLED);
       net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB);
     }
     // else CompleteRequests logged EndEvent.
-
     if (!requests_.empty()) {
       // Log any remaining Requests as cancelled.
       for (RequestImpl* req : requests_) {
         DCHECK_EQ(this, req->job());
+        LogCancelRequest(req->source_net_log(), req->info());
         req->OnJobCancelled(this);
-        LogCancelRequest(req->source_net_log(), req->info());
       }
       requests_.clear();
     }
   }
 
   // Add this job to the dispatcher.  If "at_head" is true, adds at the front
   // of the queue.
   void Schedule(bool at_head) {
     DCHECK(!is_queued());
     PrioritizedDispatcher::Handle handle;
@@ skipping 1270 matching lines @@
   if (job_)
     job_->CancelRequest(this);
 }
 
 void HostResolverImpl::RequestImpl::ChangeRequestPriority(
     RequestPriority priority) {
   job_->ChangeRequestPriority(this, priority);
 }
 
 }  // namespace net